1. Field of the Invention
This invention relates to a method for treating wastewater containing active sludge, more particularly to a method using a filter media for treating wastewater containing active sludge.
2. Description of the Related Art
Solid-liquid separation membrane bioreactors have been used in wastewater treatment. The membranes employed in the membrane bioreactors can be ultra-filtration membranes or micro-filtration membranes based on the actual requirements for separating bio-sludge thus formed from the bio-treated wastewater. Since the concentration of the sludge in a body of the bio-treated wastewater is relatively high, the membrane tends to be easily blocked by the sludge.
Non-woven materials have been used for the membranes. However, since the non-woven material is formed of a net-like structure of stacked fibers, particles present in the wastewater are easily trapped in pores in the net-like structure of the stacked fibers. As a consequence, undesired fouling can easily occur, thereby considerably lowering the membrane flux of the membrane. To alleviate fouling, a porous polymeric coating applied to a non-woven substrate has been proposed. However, since the polymeric coating is porous, its mechanical strength is relatively poor. Moreover, the polymeric coating has a tendency to peel from the non-woven substrate.